Signaling system



June l5, 1937.- w. RUNGE 2,083,747

SIGNALING SYSTEM Original Filed April 25, 1931 cos. (0/

IMAM 11mm M3. 29% bus. )5.

- INVENTOR v WlLHELM/PNGE BY ATI'ORNEY Patented June 15, 1937 UNITEDSTATES SIGNALING SYSTEM Wilhelm Runge, Berlin, Germany, assignor toTelefunken Gesellschaft fiir Drahtlose Telegraphic In. b. H., Berlin,Germany, a corporation of Germany Application April 25, 1931, Serial No.532,971. Renewed April 8, 1936. In Germany April 28,

' 14 Claims.

' A transmitter, whose energy is altered at the rate or rhythm. of someaudio frequency signals, sends out not only the carrier frequency atwhich it is excited, but, as a result of the action of the amplitudevariations on the carrier frequency, also sends out additionalfrequencies known as the side-band frequencies, which are produced aboveand below the so-callcd carrier wave or frequency. If the transmitter ismodulated with a mixture of frequencies, as in the case of voicemodulation, there arises an upper and a lower side band frequency foreach such modulating frequency. For this reason one speaks of the upperand the lower side band rather than of individual or distinctfrequencies. To each frequencyin the upper side band there corresponds afrequency in the lower side band, both of which result from the samemodulating frequency and on reception of the signal both furnish thesame demodulated frequency. Hence, in order to transmit signals, but oneof the said two side bands is required. It is a suggestion well known inthe prior art to narrow down the aggregate frequency band required'or atleast occupied by a modu- Q5 lated sender by sending out only thecarrier wave and one side band, while the other side band is suppressed.I

The carrier wave itself does not contain any thing of the frequencies tobe transmitted. Fun- .3 darnentally speaking, it is thus admissible toomit thesame in transmissions, and to generate it locally at thereceiving end and thereupon add it.' Such addition of the carrier to oneside-band is especially simple if upon transmission not only thecarrier, but also one side band, have been omitted. By cutting out thecarrier wave, a large amount of the energy which is otherwise ex pendedat the sending .end will be saved.

In the light of what has been pointed out above, it is desirable toprovide ways and means whereby in the'sending of modulated oscillations,one side-band may be suppressed, so that only the carrier wave and theother side-band are transmitted, or whereby thefcarrier wave and onesideband are suppressed, with the result in the latter instance thatonly one side-band is sent out.

The circuit for, and the method of signaling in accordance with thepresent invention, will be better understood by the following detaileddescription thereof and therefrom when read in connection with thedrawing, in which:

Fig. 1 shows, merely for purposes of illustration, a circuit arrangementwhereby phase modulation of a carrier wave may be accomplished. Fig. 1serves to describe and illustrate the principle of applicants invention;while Fig. 2 shows a phase modulator similar to the arrangement of Fig.1, in which novel means 60 have been added for accomplishing amplitudemodulation of the carrier and combining the same with the phasemodulated wave.

According to the invention this is accomplishable in the following way.If the amplitude of an oscillation is controlledat audio frequencyrhythm, then, in addition to the carrier wave, there arise two sidefrequencies. If, on the other hand, the amplitude of an oscillation isleft entirelyconstant, while the phase is altered at the rate or rhythmof the audio frequency to be transmitted, then, in addition to thecarrier wave, there are set up also two side-band frequencies. It can beshown that if conditions are conveniently chosen the carrier frequencyand one side frequency can be made the same as to amplitude and phase asthose which arise by amplitude modulation, while the other sidefrequency has phase opposite that obtained in amplitude modulation. Thesum total of oscillations modulated by two such dissimilar modulationmethods there fore contains the carrier wave and one side band onlyinasmuch as the other side-band occurs in both modulation methods withopposite signs. The difference of both oscillations modulated in thisdifferent manner contains only one sideband, the carrier and therespective second side band occurring in both modes of modulation withthe same sign so that they drop out in the difference. This situation isdemonstrated by the following calculation:

An oscillation whose amplitude has been modulated, obeys this law:

In this expression, the first sum at the right of the equality sign isthe carrier oscillation, the second one the lower side frequency, andthe third one the upper side frequency.

Acting upon the phase by the audio frequency, the current transmittedobeys this formula:

U p:SlI1 (wt-i-go COS ft) (3) This expression is expressible also inthis way:

Uo sin wt cos cos it) cos wt sin ((p cos it) (4) Making (,0 less than/2, then the coefficient of sin wt can be put equal to unity withsufficient correctness, while in the coefiicient of cos w the sine maybe put equal to its arc. Then:

'Ugo sln wt-l-cos wt 1 cos ft. Resolving the product cos.cos, then: Up=slll wt+ p COS (w-f) t+ /z p COS (w-l-Di (6) In this latter expressionsin of denotes again the carrier wave to be modulated; w-f is the lowerside frequency, w+f the upper side frequency, while (,0 in analogy withthe amplitude modulation, can be designated as the phase modulationdegree.

Comparing the final formula for Ua and for Ugo it will be seen that, ifgo k the two expressions in the carrier frequency and the lower sidebandagree as to frequency, phase and amplitude, whereas in the upper side,band, while there is agreement as to frequency and amplitude, thereoccur different signs. The sum total of both oscillations therefore is:

It includes the carrier frequency and the lower side-band frequency, theupper side frequency has been eliminated. The difference between bothoscillations becomes:

Ua cos (w+f) t The carrier and one side-band have been eliminated.

For practicing phase modulation and amplitude modulation, as outlinedabove, recourse may be had to different circuit schemes. Althoughapplicant does not wish to limit himself to specific circuitarrangements, except as marked out in the claims below, severalarrangements illustrative of the invention will be described.

One embodiment is shown in Figure l. The grid electrodes of two tubes iand 2 are fed with carrier wave potentials cos of and sin of displacedby 99 degrees. The two tubes are modulated push-pull-fashion by theaudio frequency energy by way of transformer T. The audio frequencypotentials are applied to the control grids of tubes i and 2differentially, that is, out of phase, as shown. Phase modulation isaccomplished and phase modulated signals appear in the transformer K.This has been shown mathematically above but will perhaps be morereadily understood from the following, if we visualize the vectors andresultant of the carriers and modulating frequencies combined. Assume wedraw a vector of a length E1 to represent sin of and from the sameorigin a vector E2 displaced to represent cos of. The resultant will liebetween these two vectors. Now the modulation potentials are applieddifferentially to the grids of the tubes i and 2. When one rid rises inpotential the other falls. The vec tors sin of and cos of willalternately decrease and increase in length and the resultant will shiftbetween these two vectors. This is phase modulation unaccompanied bymaterial amplitude modulation since the length of the resultant will notchange to a great extent. The plates of both tubes are connected inparallel and the cur- .rents in their circuits flow through a jointcoupling transformer K with which the output or utilization circuit maybe coupled.

Another embodiment of an assembly is shown by way of example in Figure2. From the radio frequency oscillator 0 tubes 1 and 2 are supplied bycarrier wave potentials displaced by an angle of 90 degrees. Audiofrequency modulation as before takes place through transformer T. 3denotes the tube in which the carrier oscillations are modulated inamplitude. The output circuits of tubes 5, i2 and 3 act by way ofcoupling transformers Kl, K2 upon a joint circuit. In the transformer K1we have phase modulation produced in the same manner in which phasemodulation was produced in Figure 1. In the transformer K2 we haveamplitude modulation. Here an object is to eliminate a carrier and aside band so that we have left a single side band for transmission. Themanner in which this is accomplished will be clear if we consider thecarrier and side bands resulting from amplitude and phase modulation. Aspointed out hereinbefore (page 1, seventh paragraph, and Equations 2 anda), if the components resulting from phase modulation and amplitudemodulation are added the side bands of unlike sign cancel and we have acarrier and side band left which are the sum of the carriers and sidebands resulting from the phase and amplitude modulation. If we take thedifference of the energies resulting from phase and amplitude modulationunder proper conditions, that is, when the two carriers are out ofphase, so that they cancel, we have left but one side band which is thesum of one of the side bands resulting from phase modulation and one ofthe side bands resulting from amplitude modulation. Conditions are suchin the circuit of Figure 2 as to produce this single side band in theoutput circuit. It is also feasible to obtain the desired effect whenone and the same carrier is consecutively modulated in phase and inamplitude. In this instance, only one side-band will be suppressed.

If the output circuits of tubes I, 2, and 3 are properly arranged thephase modulated and amplitude modulated outputs may be added or combinedto produce a carrier and one side band for signaling purposes.

Having thus described my invention and the operation thereof, what Iclaim is:

1. The method of producing a predetermined phase difference betweenseveral portions of energy resulting from the demodulation of a carriermodulated at signal frequency which includes the steps of, modulating inphase and in amplitude carrier energy respectively by two components ofdifferent phase of the signal energy and combining the resultantmodulated energy.

2. The method as recited in claim 1 in which the resultant modulatedenergy is combined to obtain the difference of the components resultingfrom the modulation in phase and in amplitude of the carrier.

3. An arrangement for the production of mod ulated radio frequencyoscillations in which certain components are suppressed comprising, asource of potentials of signal frequency, a source of carrier frequencywaves, means connected with both of said sources for modulating thephase of the carrier frequency Waves in accordance with the signalpotentials, means connected with both of said sources for modulating theamplitude of the carrier frequency waves in accordance with theaforesaid signal potentials, and means for combining the energyresulting from said modulating steps.

4. Means for modulating carrier wave energy at signal frequency and forsuppressing from the resultant modulated energy a side-band and energyof the carrier wave frequency comprising, a thermionic relay including apair of thermionic tubes having their input electrodes connected inpush-pull relation by an input circuit and their output electrodesconnected in parallel, a circuit for impressing potentials of carrierfrequency energy of unlike phase on said input circuit, a circuit forimpressing modulating potentials on said ir dill circuit and from saidinput circuit differe; to the input electrodes of said tube, a

third thermionic tube having input electrodes, and output electrodes, acircuit for impressing carrier frequency energy of predetermined phaseon the input electrodes of said third tube, a circuit for modulating inamplitude the carrier frequency impressed on said third tube inaccordance with modulating potential of predetermined phase, and outputcircuit connected with the output electrodes in said third tube, and acircuit coupled to the output circuits of said third tube and saidfirst-named tubes.

5. A device for varying the phase of carrier frequency oscillations atsignal frequency and for maintaining the amplitude of said oscillationssubstantially constant comprising, a pair of thermionic tubes eachhaving electrodes including an anode, a cathode and a control grid,sources of carrier frequencies of unlike phase, an input circuitincluding an inductance connected between the control grid and cathodeof one of said tubes, a coupling between one of said sources and saidinductance, an input circuit including an inductance connected betweenthe control grid and cathode of the other of said tubes, a couplingbetween the other of said sources and said last named inductance, asource of modulating frequency potentials, a transformer having ase'condary winding, portions of which are in each of said inputcircuits, and a coupling between said modulation frequency source andthe primary winding of said transformer, whereby modulating potentialsare applied difierentially to the input circuits of said tubes.

6. Signaling means comprising, a circuit for producing high frequencyoscillations modulated in phase including, a pair of thermionic tubes,each having a control grid, a cathode and an anode, a circuit forcoupling the anodes of said tubes in parallel, circuits for applyingcarrier frequency oscillations of unlike phase but of like frequency tothe control grids of said tubes, a circuit for applying modulatingpotentials differentially to the control grids of said tubes, wherebyphase modulated oscillations appear in the circuit connected with theanodes of said tubes, a third thermionic tube having an anode, a cathodeand a control grid, an output circuit connected between the anode andcathode of said third tube, means for applying carrier frequencyoscillations to the control grid of said third tube, means for applyingmodulating potentials to the control grid of said third tube, wherebyoscillations modulated in amplitude at signal frequency appear in theoutput circuit of said third tube, and a circuit for combining themodulated oscillations appearing in the output circuit of said thirdnamed tube with the modulated oscillations appearing in the outputcircuit connected with said first named pair of tubes to obtain a singleside band.

'7. The method of producing a'predetermined phase difference betweenseveral portions of energy resulting from the modulation of a carrier atsignal frquency which includes the steps of, modulating in phase and inamplitude carrier energy respectively by two components of differentphase of the signal energy and combining the resultant modulated energyto obtain the sum of the components resulting from the modulation inphase and in amplitude of the carrier.

8. The method of signaling by means of high frequency carrier waves andoscillations of lesser frequency which includes the steps of separatelymodulating the phase of the high frequency car- 75 rier waves inaccordance with said oscillations of lesser frequency, separatelymodulating the amplitude of said high frequency carrier waves with saidoscillations of lesser frequency, and combining the energy resultingfrom said modulation processes.

9. The method as recited in claim 8 in which the energies resulting fromsaid modulating steps are combined additively.

10. The method of signaling, as recited in claim 8, in which theenergies from said modulating steps are combined subtractively.

11. Signaling means comprising in combination a phase modulator, anamplitude modulator, a work circuit coupled to the output of both ofsaid modulators, a source of modulating potentials, phase displacingcircuits coupling said source of modulating potentials to each of saidmodulators, a source of carrier waves, and separate circuits one or moreof which include phase displacing means coupling each of said modulatorsto said source of carrier waves.

12. A phase modulator comprising a pair of electron discharge deviceseach having an anode, a control electrode, and a cathode, means forenergizing the control electrodes of said devices by phase displacedoscillations of like frequency, means directly connecting the cathodesof said tubes together, means directly connecting the anodes of saidtubes together, an alternating current output circuit connecting theanodes to the cathodes of said tubes, a source of modulating potentials,an impedance, a circuit connected with said source of modulatingpotentials for impressing modulating potentials on said impedance and acircuit connecting points on said impedance at which said modulatingpotentials are of unlike phase to the control electrodes of saiddevices, to thereby vary in unlike manner the conductivity of saiddevices in accordance with modulating potential variations in saidimpedance.

13. In a phase modulation system, a pair of electron discharge deviceseach having an anode, a cathode and a control grid, means connecting theanodes of said devices directly together, means connecting the cathodesof said devices directly together, an alternating current output circuitconnected between said anodes and cathodes, means for supplyingoscillations of carrier wave frequency to the control grid and cathodeof one of said devices, means for supplying oscillations of the samefrequency but of different phase to the control grid and cathode of theother of said devices and means for applying modulating potentials inphase displaced relation to the control grids of said devices.

14. In a phase modulation system a pair of electron discharge deviceseach having an anode, a cathode and a control grid, means directlyconnecting the anodes of said devices together, means directlyconnecting the cathodes of said devices together, an alternating currentoutput circuit connected between said anodes and cathodes, a circuitconnected with the control grid and cathode of one of said devices forsupplying oscillations of carrier wave frequency to the control grid andcathode of said device, a circuit connected with the control grid andcathode of the other of said devices for supplying oscillations of thesame frequency but of different phase to the control grids of saiddevices, an impedance connecting the control grids of said device inpushpull relation, said impedance being connected to the cathodes ofsaid devices, and means for applying modulating potentials to saidimpedance.

' WILHELM RUNGE.

